Coyote Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Coyote Observatory clear sky chart from 2005-11-05 to 2017-09-24.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
27%
14686
12%
46931
7%
14656
33%
14656
16%
33552

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
15%
720
5%
2506
3%
716
19%
716
6%
2041
January16th to endNight
19%
768
10%
2619
5%
768
26%
768
11%
1970
February1st to 15thNight
16%
702
8%
2287
3%
701
23%
701
10%
1751
February16th to endNight
20%
631
12%
1967
5%
631
29%
631
12%
1458
March1st to 15thNight
15%
720
10%
2076
6%
720
21%
720
14%
1563
March16th to endNight
23%
768
14%
2051
7%
768
29%
768
22%
1414
April1st to 15thNight
21%
718
14%
1796
5%
718
26%
718
19%
1323
April16th to endNight
28%
642
16%
1722
7%
642
35%
642
22%
1215
May1st to 15thNight
28%
360
14%
1440
13%
360
37%
360
16%
951
May16th to endNight
30%
375
12%
1497
9%
374
42%
374
19%
942
June1st to 15thNight
35%
360
9%
1440
8%
360
43%
360
15%
963
June16th to endNight
45%
360
8%
1440
11%
360
49%
360
18%
920
July1st to 15thNight
50%
340
14%
1360
20%
340
57%
340
27%
756
July16th to endNight
55%
376
14%
1418
15%
354
60%
354
27%
810
August1st to 15thNight
41%
470
12%
1541
10%
468
45%
468
24%
973
August16th to endNight
40%
691
16%
1837
8%
691
45%
691
36%
1135
September1st to 15thNight
44%
720
15%
1800
7%
720
46%
720
29%
1246
September16th to endNight
47%
693
21%
1893
15%
693
51%
693
31%
1212
October1st to 15thNight
31%
660
17%
1980
11%
660
40%
660
19%
1382
October16th to endNight
22%
704
10%
2181
5%
704
29%
704
12%
1663
November1st to 15thNight
25%
700
15%
2352
12%
700
32%
700
15%
1682
November16th to endNight
18%
720
8%
2520
6%
720
23%
720
9%
1953
December1st to 15thNight
16%
720
5%
2520
2%
720
20%
720
7%
2050
December16th to endNight
12%
768
8%
2688
4%
768
18%
768
8%
2179

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
17%9%36%5%34446%32%
48004
Night
17%9%46%6%34445%33%
47101
Cloud CoverDay
28%7%25%423345%31%
48014
Night
27%7%35%42333434%
47106
TransparencyDay
51%6%11%19%9%1
47692
Night
52%6%11%19%9%
46931
SeeingDay
22%12%29%21%10%3
5468
Night
22%12%29%24%9%
14688

By Month

Percentage Cloud Cover NE (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
19%14%5%9%8%2444322%
1432
16th to endDay
14%14%5%10%9%35%445%22%
1605
February1st to 15thDay
12%13%6%13%8%35%42423%
1575
16th to endDay
17%13%5%7%7%45%34426%
1504
March1st to 15thDay
17%11%48%7%45%33426%
1871
16th to endDay
14%9%45%434445%40%
2172
April1st to 15thDay
22%11%36%423435%33%
2152
16th to endDay
20%8%26%424345%36%
2249
May1st to 15thDay
20%8%36%5%24346%33%
2511
16th to endDay
17%6%35%5%345%46%35%
2618
June1st to 15thDay
21%7%35%5%3445%6%31%
2520
16th to endDay
17%6%25%6%35%5%6%7%33%
2520
July1st to 15thDay
12%6%25%436%5%7%8%37%
2520
16th to endDay
11%425%6%35%6%7%10%35%
2654
August1st to 15thDay
12%6%27%6%36%5%6%7%37%
2407
16th to endDay
12%5%25%5%35%5%6%7%40%
2352
September1st to 15thDay
17%5%245%24447%40%
2160
16th to endDay
14%425%33345%6%45%
1924
October1st to 15thDay
22%8%35%5%34446%32%
1650
16th to endDay
26%9%37%6%4443425%
1689
November1st to 15thDay
15%10%36%4345%46%34%
1503
16th to endDay
21%12%5%7%5%45%345%23%
1440
December1st to 15thDay
20%16%5%9%7%45%44416%
1440
16th to endDay
22%16%6%8%6%2443420%
1536
January1st to 15thNight
16%14%7%11%8%35%5%4417%
2506
16th to endNight
13%15%5%8%8%25%435%26%
2619
February1st to 15thNight
12%14%7%10%7%35%446%23%
2285
16th to endNight
15%10%5%7%7%3445%6%28%
1967
March1st to 15thNight
17%12%6%8%6%33335%30%
2064
16th to endNight
14%7%45%5%33445%40%
2051
April1st to 15thNight
23%7%36%433345%34%
1796
16th to endNight
18%9%25%6%23445%37%
1722
May1st to 15thNight
21%8%3442334438%
1440
16th to endNight
15%5%245%35%5%5%7%39%
1495
June1st to 15thNight
17%6%36%435%5%46%36%
1440
16th to endNight
15%5%25%5%35%5%6%7%38%
1440
July1st to 15thNight
9%434425%5%48%47%
1440
16th to endNight
9%41443447%8%46%
1514
August1st to 15thNight
9%425%5%345%6%8%43%
1551
16th to endNight
9%4244245%47%50%
1837
September1st to 15thNight
16%6%25%5%33446%42%
1800
16th to endNight
15%5%24422245%49%
1893
October1st to 15thNight
21%7%35%42435%6%35%
1980
16th to endNight
23%10%37%5%25%445%26%
2181
November1st to 15thNight
19%9%35%6%24445%32%
2352
16th to endNight
21%13%5%9%6%2434424%
2520
December1st to 15thNight
20%17%5%8%6%35%44419%
2520
16th to endNight
23%15%6%9%6%2434420%
2688

Percentage Cloud Cover SE (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
21%14%6%7%6%3334424%
1432
16th to endDay
15%14%5%9%8%35%44424%
1605
February1st to 15thDay
19%12%5%11%7%2442325%
1575
16th to endDay
23%12%46%7%3434325%
1504
March1st to 15thDay
40%5%25%42322326%
1882
16th to endDay
40%5%1221222333%
2171
April1st to 15thDay
32%7%2431232334%
2152
16th to endDay
31%5%24312345%36%
2249
May1st to 15thDay
40%6%2431223329%
2511
16th to endDay
38%41331223433%
2618
June1st to 15thDay
33%5%24433335%30%
2520
16th to endDay
31%413424445%32%
2520
July1st to 15thDay
13%5%24435%5%7%9%39%
2520
16th to endDay
12%415%5%346%7%9%38%
2654
August1st to 15thDay
38%314434345%26%
2407
16th to endDay
39%313323335%31%
2352
September1st to 15thDay
21%424423337%41%
2160
16th to endDay
19%424323445%44%
1924
October1st to 15thDay
24%7%34434445%33%
1650
16th to endDay
28%8%47%5%3433428%
1689
November1st to 15thDay
25%8%2422332438%
1503
16th to endDay
28%9%5%5%43323429%
1440
December1st to 15thDay
25%14%5%8%7%3443419%
1440
16th to endDay
26%15%5%6%5%2343323%
1536
January1st to 15thNight
20%12%5%9%7%35%44323%
2506
16th to endNight
17%13%5%7%6%2443329%
2619
February1st to 15thNight
21%13%5%8%6%2334425%
2278
16th to endNight
25%9%37%6%2434429%
1967
March1st to 15thNight
42%6%3431222327%
2076
16th to endNight
40%41332222334%
2051
April1st to 15thNight
30%5%25%41212439%
1796
16th to endNight
24%6%3432234440%
1722
May1st to 15thNight
36%5%1331222337%
1440
16th to endNight
30%413313335%39%
1495
June1st to 15thNight
23%5%25%42334439%
1440
16th to endNight
21%41442445%5%40%
1440
July1st to 15thNight
10%325%42445%8%48%
1440
16th to endNight
10%41443346%8%48%
1514
August1st to 15thNight
33%313313345%35%
1551
16th to endNight
34%21221223440%
1837
September1st to 15thNight
19%5%24424345%44%
1800
16th to endNight
19%414322235%50%
1893
October1st to 15thNight
24%6%35%423335%37%
1980
16th to endNight
27%8%36%5%24335%30%
2181
November1st to 15thNight
33%7%2432222334%
2352
16th to endNight
35%9%35%41222328%
2520
December1st to 15thNight
28%13%36%5%3343325%
2520
16th to endNight
30%13%38%5%2333323%
2688

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
65%5%10%12%5%1
1433
16th to endDay
64%5%10%12%7%
1605
February1st to 15thDay
64%5%10%14%4
1577
16th to endDay
61%5%9%13%9%1
1504
March1st to 15thDay
60%5%11%15%6%
1882
16th to endDay
45%5%8%19%15%5%
2172
April1st to 15thDay
54%47%18%13%2
2152
16th to endDay
48%48%18%16%3
2249
May1st to 15thDay
51%5%8%17%14%2
2511
16th to endDay
47%7%12%19%12%1
2622
June1st to 15thDay
52%7%10%20%9%
2520
16th to endDay
47%8%12%19%11%1
2520
July1st to 15thDay
37%8%15%25%12%
2371
16th to endDay
41%9%16%22%9%
2487
August1st to 15thDay
43%9%15%21%10%
2393
16th to endDay
39%8%16%25%9%
2352
September1st to 15thDay
42%6%12%26%11%
2160
16th to endDay
38%7%12%31%9%
1924
October1st to 15thDay
52%6%11%19%9%
1650
16th to endDay
62%6%11%13%5%
1689
November1st to 15thDay
48%7%15%20%8%
1503
16th to endDay
62%6%11%12%5%1
1440
December1st to 15thDay
69%7%11%9%2
1440
16th to endDay
66%6%11%10%4
1536
January1st to 15thNight
68%5%9%10%4
2506
16th to endNight
59%5%10%16%7%
2619
February1st to 15thNight
61%5%12%15%4
2287
16th to endNight
55%6%10%17%8%
1967
March1st to 15thNight
57%411%18%7%
2076
16th to endNight
45%49%20%15%3
2051
April1st to 15thNight
52%48%18%14%1
1796
16th to endNight
48%48%18%16%3
1722
May1st to 15thNight
48%5%8%18%14%3
1440
16th to endNight
42%7%13%19%14%2
1497
June1st to 15thNight
48%7%12%20%10%1
1440
16th to endNight
43%8%14%19%14%
1440
July1st to 15thNight
32%7%13%29%15%1
1360
16th to endNight
33%8%17%25%15%
1418
August1st to 15thNight
36%10%16%23%12%
1541
16th to endNight
31%6%16%32%11%
1837
September1st to 15thNight
41%6%12%27%10%1
1800
16th to endNight
37%5%12%34%9%
1893
October1st to 15thNight
48%6%11%20%12%
1980
16th to endNight
58%6%13%14%6%
2181
November1st to 15thNight
52%6%12%17%10%
2352
16th to endNight
62%6%11%15%3
2520
December1st to 15thNight
66%6%12%10%3
2520
16th to endNight
68%5%9%11%5%
2688

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
28%28%18%20%5%
60
16th to endDay
36%13%36%13%1
75
February1st to 15thDay
33%22%35%8%
90
16th to endDay
32%23%25%14%4
163
March1st to 15thDay
26%18%32%17%4
270
16th to endDay
23%18%29%17%9%1
288
April1st to 15thDay
27%22%27%14%7%
270
16th to endDay
24%19%25%16%10%3
270
May1st to 15thDay
30%12%27%16%8%3
288
16th to endDay
23%12%34%18%8%1
331
June1st to 15thDay
26%9%32%19%9%1
315
16th to endDay
17%11%33%24%12%1
315
July1st to 15thDay
15%430%29%13%5%
305
16th to endDay
11%6%30%31%15%4
326
August1st to 15thDay
13%6%24%34%12%7%
313
16th to endDay
14%5%26%27%15%10%
332
September1st to 15thDay
17%7%26%18%18%12%
315
16th to endDay
14%9%26%19%19%10%
287
October1st to 15thDay
25%10%25%25%9%2
255
16th to endDay
31%17%28%15%6%
259
November1st to 15thDay
25%10%31%22%8%1
157
16th to endDay
35%16%33%10%5%
60
December1st to 15thDay
16%25%38%18%1
60
16th to endDay
43%21%31%3
64
January1st to 15thNight
24%19%34%17%4
720
16th to endNight
21%15%35%22%4
768
February1st to 15thNight
19%16%38%21%3
704
16th to endNight
21%19%32%21%5%
631
March1st to 15thNight
26%15%32%22%3
720
16th to endNight
19%16%29%24%9%
768
April1st to 15thNight
26%16%29%21%5%
718
16th to endNight
25%14%28%22%8%
642
May1st to 15thNight
27%7%26%27%9%1
360
16th to endNight
17%7%36%25%12%
375
June1st to 15thNight
20%8%30%30%9%
360
16th to endNight
17%6%27%36%12%
360
July1st to 15thNight
8%427%41%16%1
340
16th to endNight
9%126%45%14%1
376
August1st to 15thNight
11%423%38%19%1
470
16th to endNight
11%424%35%20%2
691
September1st to 15thNight
18%5%25%28%19%2
720
16th to endNight
16%8%22%25%23%3
693
October1st to 15thNight
25%10%28%23%11%1
660
16th to endNight
29%14%26%22%6%
704
November1st to 15thNight
24%11%31%21%10%
700
16th to endNight
31%17%24%18%6%
720
December1st to 15thNight
29%17%31%17%3
720
16th to endNight
33%13%31%16%3
768
Page generated at 2017-09-25 09:02:28. Version ac04

Copyright 2017 A. Danko


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